The invention relates to a suction sound damper for a hermetically encapsulated compressor, having a housing that is formed of at least an upper part, a lower part and an insert, and having at least two chambers and a channel, connected thereto, leading from a lower inlet opening to an upper outlet opening.
In a known suction sound damper of that type (U.S. Pat. No. 5,201,640), which is designed for hermetically encapsulated small refrigerating machines, as used in household refrigerators and the like, the inner area is divided into two chambers by a vertical wall. With the aid of an insert a channel is formed which alters the direction of flow of the suction gas several times. The upper part has an extension that contains the final channel section and fits into a recess in the cylinder head cover so that the entire suction sound damper can be secured to the cylinder head.
From U.S. Pat. No. 3,750,840 there is known a sound damper for a hermetically encapsulated compressor in which a pot-shaped lower part and a pot-shaped upper part are pushed over one another telescopically and are welded to one another. Held in the lower part is an insert that divides the inner area of the sound damper into an upper and lower chamber and, together with a shaped piece of sheet metal, forms a throttle channel between the two chambers. Input is effected by way of a tube positioned at the top and the outlet is effected by way of a laterally adjoining tube at the bottom.
From U.S. Pat. No. 3,220,506 there is known a sound damper for internal combustion machines that release water and gas. Two pot-shaped parts are inserted into one another horizontally and receive between them the flange of a similarly pot-shaped insert. There remains between the insert and the outer structural part an annular space into which water and exhaust gases from the motor are fed by way of holes in the flange of the insert.
The problem underlying the invention is to provide a suction sound damper of the type described at the beginning that provides improved sound damping.
The problem is solved according to the invention by the fact that the insert has a side wall that together with a section of the housing wall forms a capillary gap in which lubricating oil collects and is retained.
In that construction the oil layer in the capillary gap provides extra damping in addition to the other damping measures. Since the suction gas always entrains a certain amount of lubricating oil with it, the capillary gap automatically fills up with oil after a short period of operation.
It is advantageous for the capillary gap to be located at a two-dimensionally curved section of the housing wall. Firstly, the capillary gap can be formed with high precision when the curvature is two-dimensional. Secondly, two-dimensionally curved wall sections are at substantially greater risk of vibratory excitation than are three-dimensionally curved wall sections. The damping is therefore effected directly at the location at which the sound radiation occurs.
It is recommended that the insert divide the inner area of the housing into an upper chamber and a lower chamber. The simple structural shape can therefore be retained even when the side wall necessary to form the capillary gap is used.
It is advantageous for the capillary gap to be open towards the lower chamber. Since the capillary gap also fills up from below, this results in great freedom of design. In particular, the upper chamber can be made to be relatively large and in any case larger than the lower chamber, which improves the degree of filling.
In a further construction the insert is provided with a base that is inclined to the horizontal and at the lowest point has a discharge opening leading to the lower chamber. Any oil deposited in the upper chamber is immediately drained away below.
In a further construction the lower part is provided with a base that is inclined to the horizontal, the lowest point of which is connected to the inlet opening. Oil that has reached the lower chamber can be drained off by way of the inlet opening.
It is also advantageous for the lower part to have a first channel section connected to the inlet opening, for the insert to have a tube-shaped second channel section and for the upper part to have a third channel section connected to the outlet opening. Each of the three structural parts (lower part, insert, upper part) thus has a channel section. The complete channel is then produced automatically when the three parts are assembled together.
It is recommended that the three channel sections be arranged approximately in a straight line. This means that the gas that is drawn in can flow virtually in a straight line from the inlet opening to the outlet opening. The losses of flow are correspondingly small and the degree of filling of the compressor is correspondingly high.
An especially simple option for connecting the channel to the chambers is for the channel sections to be arranged spaced from one another or for the channel walls to be provided with radial openings.
In a further construction of the invention, the insert has, in addition to the tube-shaped second channel section, a laterally offset connecting opening between the two chambers. That connecting opening results in a phase shift in the build-up of pressure in the suction sound damper and can be so constructed in terms of its position, size and shape that pressure pulses are reduced at least to some extent by interference.
It is also advantageous that the volume of the chambers be sufficiently large that the compressor stroke chamber during the suction stroke is filled essentially wholly by gas contained in the suction sound damper. The suction sound damper then serves as a suction gas reservoir, which means that the suction gas has to travel only a short path to the stroke chamber of the compressor and not from the inlet of the suction sound damper. The resistance to suction is correspondingly low and the degree of filling of the compressor is correspondingly high.
It is advantageous for the upper part and lower part to be connected to one another at flanges and receive between them a flange of the insert. This form of assembly known per se ensures precise association of the individual parts with one another.
In a preferred embodiment, moreover, the upper part is provided with a tube-shaped extension that fits into an indentation in the cylinder head cover, and with a three-point support for contact against the valve plate of the compressor or against a seal arranged between the cylinder head cover and the valve plate, which seal encloses the contact surfaces of the outlet opening and of two supports, at least one of which is spaced from the tube-shaped extension. The three-point support provides an especially secure position of the suction sound damper on the compressor head.